The present invention relates to marine drives, and more particularly to a valve for automatically draining the cooling water from a marine engine when the engine is stopped.
Various types of drain valves are typically used in a marine environment. For example, drain valves referred to as "self-bailers" or automatic bilge valves for attachment to the bottom of a boat which operate on the suction principle are well known. Such bailers typically include an exhaust aperture which, in use, is directed toward the rear or stern of the boat. Water collecting in the boat is discharged through the exhaust aperture by means of suction created by movement of the boat through the water. Examples of such devices may be found in the following U.S. patents: No. 271,060 to Graham; No. 2,655,121 to Cuneo; No. 2,884,888 to Pugol; No. 2,959,144 to Youtie; No. 2,966,875 to Irey; No. 3,011,468 to O'Gara; No. 3,067,714 to Allmand; and No. 3,875,888 to Bier.
Drain valves, however, have not been up to this point commonly used with recreational marine drive engines which utilize seawater for cooling. In standard arrangements, cooling water drainage is accomplished by allowing gravity to cause the cooling water to flow out of the engine through an orifice in the engine housing which is always open. Nevertheless, in several prior known marine drive engines, namely, the "MerCruiser", 60, 80, and 90 engines sold by the assignee of the present invention, there was used a floating plastic ball for opening and closing a drain circuit. These plastic balls floated upward within a ported cavity to close the drain circuit when cooling water was pumped to the engine. In turn, when the water pump stopped, gravity caused the cavity containing the ball to drain thus uncovering the drain circuit and draining cooling water from the engine.
Such floating ball drain valves have several inherent disadvantages due to their principle of operation. Most noticeably, the forces which made the ball float were relatively small making the valve's operation erratic when the environment departed from a new, clean condition. Since the ball chamber was directly in the flow path of the cooling water it could "see" any debris ingested by the pump, and, because of the chamber's shape, the debris could be accummulated in the chamber to the extent that the ball's desired motion was either impeded or prevented. The result was to produce either overheating or loss of drainage depending upon the ball's position at the time of debris accummulation. A loss of drainage also could result in accelerated corrosion if the engine is being used in salt water.